A communication bus, which may be consist of a computer backplane, a board bus, an on-chip bus within an integrated circuit, a local area network or LAN, a wide area network or WAN, or other type of bus, allows data (e.g., control, timing and/or data signals) to be transferred between the various components and/or devices that comprise the system. Of particular interest in the automotive industry is the controller area network, or CAN, bus. The CAN bus is a multi-master broadcast serial bus that may be implemented using balanced pair signals in twisted-pair wires, optionally in shielded cables.
In a typical, electrically isolated communication bus, power must be applied to both the bus master and the slave node(s) before a signal can cross the isolation barrier. This approach results in a continuous power drain which, in a power sensitive application such as an electric vehicle, is quite undesirable as it may impact vehicle range and performance. One technique that has been employed to reduce power drain is to turn off all unnecessary circuits in the slave node when the slave node is in a sleep mode and only activate these circuits when the slave node receives a wake-up signal from the bus master. In another approach, a further reduction in power drain is achieved by cycling the receiver circuit of the slave node on and off. This approach, however, results in increased wake latency since the wake-up signal must occur when the receiver circuit is powered up.
Accordingly, what is needed is a communication bus that allows a slave node to be completely powered down and then remotely activated by the system master. The present invention provides such a communication bus design.